2 BULLETIN 741, U. S. DEPARTMENT OF AGRICULTURE. 



Beneath the aspen, which ordinarily grows in rather open stands, is 

 usually a luxuriant understory of grasses, weeds, and browse that 

 is grazed with relish by all kinds of live stock. As range land, the 

 aspen type is much more valuable than either the spruce-fir type 

 just above it or the oak-brush type just below it. Unfortunately, 

 however, the stock, especially sheep, do not confine themselves to 

 the forage, no matter how abundant and palatable it may be; they 

 also eat the foliage and tender twigs of the young aspen. This, of 

 course, means that the aspen reproduction is often badly injured or 

 even killed, which makes it very difficult in many cases to secure a 

 second stand of timber. 



A study, the results of which are presented in this bulletin, has been 

 made to determine the extent of injury to aspen reproduction by sheep 

 and cattle, the effects of such damage on the development of the . 

 young trees, and the best method of protecting the reproduction from 

 injury without unnecessarily restricting the grazing of live stock. 

 Though the results are meant to apply especially to conditions in 

 the National Forests, they may also be of value, possibly with slight 

 modifications, in the case of farm woodlands in the East where the 

 forage under aspen is converted into meat or butter fat. 



METHOD. 



The study, which covered a period of five years (1902 to 1916 inclu- 

 sive), was conducted on the Manti National Forest, in central Utah, 

 where the timber and forage are typical of the commercial aspen 

 type in National Forests. 



A general study was made on 122 sample plots in virgin and 

 lightly thinned aspen, at elevations between 7,500 and 10,000 feet, 

 in both sheep and cattle ranges and covering all variations in timber 

 and forage. 



A detailed study of the extent and growth of aspen reproduction 

 and the extent of its injury by stock and other agencies was made 

 on selected clear-cut areas, four of which were located on sheep range 

 and two on cattle range. Two of the plots on the sheep range and 

 one on the cattle range were securely fenced against stock (Plate I) ; 

 the others were left open to grazing. The reason for selecting clear- 

 cut areas for the intensive study of reproduction is that aspen repro- 

 duces mainly by sprouts from the roots of older trees and the best 

 method of harvesting mature aspen is to cut the timber clear. 



On each clear-cut area transect and quadrat sample plots were 

 established so that the sprouts originally observed could be definitely 

 located in future examinations. 



In 1913 and 1914 all plots were examined twice — once in June 

 and again in September. In subsequent seasons only the transects 

 and quadrats on the clear-cut areas were examined twice during a 



